1. Field of the Invention
The present invention relates to a radar apparatus, which transmits a signal wave that is spectrum-spread by using a spread code, despreads a reflected wave by using the delayed spread code, and calculates a distance from an amount of the delay, and particularly relates to a radar apparatus, which outputs alternating current signals with a simple configuration.
2. Description of the Related Art
In the past, various radar apparatuses have been widely used for detection of an object and measurement of a distance. For example, JP-A-2002-286855 discloses a radar apparatus, which measures presence or absence of, and a distance to an object exiting at a short distance such as in the ground. In this radar apparatus, a detection depth is extended without lowering a resolution, by disposing switch circuits for shutting-off/attenuating a signal path at a front end of a transmission antenna and a rear end of a reception antenna.
Also, U.S. Pat. No. 6,087,980 discloses a radar apparatus, which utilizes a single antenna by switching it at the time of transmission and at the time of reception. Thereby, U.S. Pat. No. 6,087,980 realizes preventing a noise component from wrapping around between a transmission side and a reception side, and cost reduction.
Further, US2001/035838A discloses a radar apparatus, which removes a low frequency component generated at the time of frequency modulation of a transmission signal, by use of a filter and a switch, and realizes high accuracy demodulation, which is not influenced by output fluctuation of the transmission signal.
Also, JP-A-2002-228745 discloses a radar apparatus, which switches a plurality of reception side paths with using a switch and stops the switching during such a period that there is no necessity to process a reception signal, and reduces electric power consumption and a heat release amount.